former navy s.e.a.l. chris kyle, who claimed a record 150 kills in iraq, died at the hands of another vet authorities say. allegedly using a semiautomatic handgun. what police don't know yet is why. >> i don't thank we'll ever know. he's the only one that knows that. but at this point, he hasn't made any comments to law enforcement as to why he did. >> reporter: kyle's friend, chad littlefield, and the suspect, eddie ray routh, all drove to the gun range together in a pickup truck. less than two hours later, kyle and littlefield were dead. routh fled to his sister's house, and she called police and he was eventually caught. routh is an iraq war veteran, leaving the marines in 2010. kyle, who wrote "american sniper" talked about his duty to those he served with is ktvt last year. >> my only regret, the guys i couldn't save. every shot i took, i felt extremely justified. >> reporter: kyle became a fierce advocate for vets, starting a foundation to help those suffering from ptsd. that may be why kyle and lit